Optical lens preform, optical lens, and method of making optical lens

ABSTRACT

The method of making an optical lens in accordance with the present invention comprises an optical lens preform producing step of producing an optical lens preform  40  having a plurality of curved surface parts  43  formed parallel to each other, and a pair of flanges  48  formed on both sides of the plurality of curved surface parts  43;  a drawing step of drawing the optical lens preform  40;  and an optical lens producing step of producing an optical lens  1  by cutting the drawn optical lens preform  40;  wherein the plurality of curved surface parts  43  of the optical lens preform  40  drawn by the drawing step function as an optically effective part. In such a method, the form of the optically effective part can be determined in the stage of the preform before drawing, whereby the optically effective part can be processed in a sufficiently large size.

TECHNICAL FIELD

The present invention relates to an optical lens acting on light emittedfrom a light-emitting device, and a method of making the optical lens.

BACKGROUND ART

Japanese Patent Publication No. 3121614 and U.K. Patent PublicationGB2108483A disclose methods of making a microlens by drawing. Such amethod forms a cylindrical preform, and heats and draws the preform,thereby forming a cylindrical lens having a cross-sectional formidentical to that of the preform.

DISCLOSURE OF THE INVENTION

The inventor studied the prior art mentioned above and, as a result, hasfound the following problem. Namely, such a conventional type method ofmaking an optical lens has been inconvenient in that the preform deformsby generating distortions and the like in the process of drawing,whereby an optically effective part acting on the light may not beformed as designed.

In order to overcome the problem mentioned above, it is an object of thepresent invention to provide a method of making an optical lens whichcan restrain the preform from being deformed by drawing. It is anotherobject of the present invention to provide an optical lens comprising anoptically effective part accurately acting on light.

The present invention provides an optical lens preform for drawing, theoptical lens preform being constructed by a light-transparent materialinto a columnar form comprising first to fourth side faces; at least oneof the first side face and the third side face opposite from the firstside face including a curved surface part formed parallel to a columnaxis, and a pair of flanges formed on both sides of the curved surfacepart.

Since corner parts which are likely to deform under the influence ofheating due to drawing are formed with a pair of flanges in such anoptical lens preform, the pair of flanges are influenced by the heating,whereas each curved surface part acting as an optically effective partcan be kept from being influenced.

Here, the “column axis of the columnar form” refers to a line segmentpassing the geometric center of gravity in each of the upper face 41 aand bottom face 41 b (see FIG. 1A) of the preform.

The curved surface part may be constituted by a plurality of curvedsurface parts arranged in contact with each other.

Preferably, any cross section perpendicular to the column axis of theoptical lens preform is oblong. As a consequence, the second and fourthside faces become parallel to each other, thereby making it easier tocarry out an optical lens arranging step which will be explained later.Here, “oblong” refers to a form which is considered oblong if the firstand third curved surfaces are assumed to be planar without takingaccount of the curved surface parts formed therein. For example, itencompasses the form indicated by the upper face 41 a in FIG. 1A.

The curved surface part may be formed as an aspheric surface.

Preferably, each flange has a projection protruded beyond the curvedsurface part. As a consequence, when drawing the optical lens preform bya roller, the optical lens preform can stably be held by way of theprojections of the pair of flanges, whereby the optical lens preform canbe prevented from wobbling at the time of drawing. The optical lens madeby drawing such an optical lens preform has projections corresponding tothose of the preform, and thus can prevent curved surface parts fromcoming into direct contact with an arrangement surface on which theoptical lens is disposed, side faces of members adjacent to the opticallens, and the like. As a consequence, curved surface parts acting onlight are harder to damage and so forth, and performances of outgoinglight are kept from lowering.

Preferably, at least one of the first and third side faces is formedinto a convex surface. When an optical lens preform is drawn, side facesthereof may be distorted so as to retract. Forming at least one of thefirst and third side faces into a convex surface can suppress theinfluence of distortion due to the drawing.

The present invention provides a method of making an optical lens, themethod comprising an optical lens preform producing step of producingthe optical lens preform; a drawing step of drawing the optical lenspreform produced by the optical lens preform producing step; and anoptical lens producing step of producing an optical lens by cutting theoptical lens preform drawn by the drawing step; wherein the curvedsurface part of the optical lens preform drawn by the drawing stepfunctions as an optically effective part acting on incident light oroutgoing light.

In such a method of making an optical lens, the form of the opticallens, the form of the optically effective part in particular, can bedetermined in the stage of the preform before drawing, whereby theoptically effective part can be processed in a sufficiently large size.Here, “acting on light” refers to changing the angle of divergence orconvergence of incident light and emitting thus changed light, orchanging the optical path of the incident light.

The optical lens producing step may include a flange cutting step ofcutting off the pair of flanges from the optical lens produced bycutting the optical lens preform drawn by the drawing step. Thisrealizes an optical lens having removed parts adversely affected bydeformation and the like upon heating in the drawing step.

The optical lens producing step may include an optical lens arrangingstep of preparing a plurality of optical lenses having the pair offlanges cut off by the flange cutting step, and arranging the opticallenses into an array by bonding the respective second and fourth sidefaces to each other. This realizes an optical lens comprising a numberof curved surface parts. Also, since a pair of flanges are cut off fromeach of the individual optical lenses arranged, an optical lens havingeliminated the adverse effects due to the heating in the drawing isrealized.

Preferably, the drawing step carries out drawing by using heating meanswith an annular form surrounding the optical lens preform produced bythe optical lens preform producing step, whereas the heating meanscomprises a ring form corresponding to a cross-sectional form in a crosssection perpendicular to the column axis of the optical lens preform.Since the heating means comprises the ring form corresponding to theform of the optical lens preform, the heating temperature does notconcentrate at corner parts of the optical lens preform. Here, the “ringform corresponding to a cross-sectional form perpendicular to the columnaxis of the preform” refers to a form in which the distance from eachside face of the preform to the heating means is the same as shown inFIG. 5B.

The optical lens in accordance with the present invention is produced byany of the above-mentioned methods of making an optical lens.

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawings.They are given by way of illustration only, and thus should not beconsidered limitative of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A to 1C are schematic views showing respective steps in themethod of making an optical lens in accordance with a first embodiment;

FIG. 2 is a view showing another example of drawing;

FIGS. 3A and 3B are schematic views showing respective steps in themethod of making an optical lens in accordance with a second embodiment;

FIGS. 4A and 4B are views showing effects of the methods of making anoptical lens in accordance with the first and second embodiments;

FIG. 5A is a schematic sectional view of the drawing step in the methodof making an optical lens in accordance with the first embodiment,whereas FIG. 5B is a schematic sectional view of the drawing step in themethod of making an optical lens in accordance with a third embodiment;

FIGS. 6A to 6C are views each showing an optical lens preform comprisinga single curved surface, and an optical lens produced by drawing theoptical lens preform; and

FIG. 7 is a view showing an optical lens preform suppressing thedistortion due to drawing, and an optical lens produced by drawing theoptical lens preform.

BEST MODES FOR CARRYING OUT THE INVENTION

In the following, embodiments of the present invention will be explainedin detail with reference to the drawings. In the following explanation,parts identical or equivalent to each other will be referred to withnumerals identical to each other without repeating their overlappingdescriptions.

FIGS. 1A to 1C are schematic views showing respective steps in themethod of making an optical lens in accordance with a first embodiment.As shown in FIG. 1A, an optical member made of a light-transparent glassmaterial is initially prepared, and is shaped into a quadrangular prismcomprising a first side face 44 to a fourth side face 47, thus formingan optical lens preform 40 (optical lens preform producing step). Anycross section perpendicular to the column axis of the optical lenspreform 40 is in the same oblong form. Therefore, the first side face 44and third side face 46 are parallel to each other, the second side face45 and fourth side face 47 are parallel to each other, the first sideface 44 and second side face 45 are at right angles, and the third sideface 46 and fourth side face 47 are at right angles.

The first side face 44 and third side face 46 are formed with aplurality of curved surface parts 43, parallel to the column axis, incontact with each other. The plurality of curved surface parts 43 areconvex surfaces, and function as an optically effective part acting onincident light or outgoing light after being drawn. The convex surfacesmay be aspheric surfaces. Each of the first side face 44 and third sideface 46 is further formed with a pair of flanges 48 on both sides of theplurality of curved surface parts 43 (at corner parts of the opticallens preform 40). Though the corner parts of the optical lens preform 40are likely to deform and so forth under the influence of the heating inthe drawing step, the plurality of curved surface parts 43 themselvesare less likely to be influenced by the heating in the optical lenspreform 40 in accordance with this embodiment, since the pair of flanges48 are formed. This effect will be explained later.

Thus, in the method of making an optical lens by drawing, the form of anoptical lens to be produced, the form of the optically effective part inparticular, can be shaped in the stage of the optical lens preform 40having a sufficiently large size (e.g., a width of 5 to 6 cm and alength of 20 cm), whereby these operations can be carried out in asimple and accurate manner.

Japanese Patent Publication No. HEI 7-15521 discloses a method of makinga refractive index distribution type cylindrical lens (SELFOC lens) bydrawing. This method employs, as a preform, a high-purity silica glassrod in which the fluorine dopant amount increases stepwise from thecenter to the radially outer side, so that the refractive indexdecreases stepwise accordingly, and does not use a preform formed withan optically effective part in terms of shape as in the presentinvention. Though such a conventional method necessitates, as a step ofproducing a preform, a step of doping it with fluorine by outside plasmamethod or immersing it into a molten salt for a long time so as toeffect ion exchange, thereby forming a refractive index distribution,such a step is unnecessary in the present invention. The conventionalmethod is also different from the present invention in terms of theresulting optical lens 1 in that the light entrance and exit surfacesare not the curved surfaces of a cylindrical form and both end partsthereof are used.

Subsequently, as shown in FIG. 1B, the optical lens preform 40 shaped bythe optical lens preform producing step is melted upon heating by anelectric furnace 35 or the like acting as heating means, and is drawn soas to attain a desirable diameter (drawing step). Preferably, theelectric furnace 35 has an annular form surrounding the optical lenspreform 40, and evenly heats and melts the optical lens preform 40 fromthereabout. A temperature regulator 32 is connected to the electricfurnace 35, whereby the temperature of the electric furnace 35 can bechanged so as to adjust the drawing temperature. Feeding rollers 90 andpulling rollers 33 are used for drawing and expanding the heated opticallens preform 40. When drawing an optical lens preform having aquadrangular prism form as mentioned above, the optical lens preform 40can be prevented from twisting during drawing if the second side face 45and fourth side face 47 are held by the feeding rollers 90 and pullingrollers 33.

Also, as shown in FIG. 2, the optical lens preform 40 may be pulled bythe pulling rollers 33 for drawing.

When it is determined that the outer diameter of the optical lenspreform 40 has attained a desirable width (0.5 to 15 mm) as a result ofdrawing, the optical lens preform 40 is cut by a cutter 37 placed belowthe pulling rollers 33. This determination is carried out by a diametermeter 38 disposed upstream the pulling rollers 33. The diameter meter 38comprises a laser section for emitting laser light, a light-receivingsection for receiving the laser light transmitted through the opticallens preform 40, and an analyzing section for calculating the outerdiameter of the optical lens preform 40 from the quantity of lightreceived by the light-receiving section and the like. The optical lensformed by cutting with the cutter 37 has a rod shape with a length of 5mm to 2000 mm, which may be in a size employed as an optical lens or asize in a stage before being cut or shaved into a desirable length(optical lens producing step). The optical lens is likely to break whentoo long, and is inconvenient for cutting and shaving when too short.Though the drawn product is wound about a drum or the like when makingan optical fiber or the like, the making of an optical lens ischaracterized by cutting the drawn product as such.

Thus produced optical lens 1 has a cross-sectional form identical tothat of the optical lens preform 40 because of characteristics ofdrawing. After drawing, the optical lens, the optically effective parts43 constituted by a convex surface in particular, is not subjected toshaping except for cutting into a desirable length and grinding on theouter periphery, whereby the burden on manufacture can be alleviated. Asshown in FIG. 1C, incident light 6 is collimated or converged by theoptically effective parts 43 (curved surface parts 43 in the preformstage) formed on the light entrance side and light exit side, and thuscollimated or converged light is emitted as outgoing light 7. Here, thedirections of the incident light 6 and outgoing light 7 may be reversed.Since the optical lens 1 comprising four curved surfaces as theoptically effective part 43 is formed in this embodiment, light beamsemitted from a semiconductor laser array acting as a light-emittingdevice having four light-emitting parts arranged therein can becollimated or converged, for example, and thus collimated or convergedlight beams can be emitted.

FIGS. 3A and 3B are schematic views showing respective steps in themethod of making an optical lens in accordance with a second embodiment.These steps follow those of FIGS. 1A to 1C. In the method of making anoptical lens in accordance with the second embodiment, as shown in FIG.3A, the pair of flanges 48 are initially cut off from the optical lens 1produced in FIG. 1C (flange cutting step), so as to yield an opticallens 21. As mentioned above, the flanges 48 incur (or may incur)influences such as deformation upon heating in the drawing step.Therefore, cutting off such a pair of flanges 48 realizes an opticallens which is more compact than the optical lens 1 shown in FIG. 1C andfree of adverse effects (such as deformation) upon heating. In theoptical lens 21 in accordance with the second embodiment, as depicted,the optically effective part 43 comprises four convex surfaces 43,whereby respective light beams emitted from four light-emitting partsarranged in a light-emitting device can be converged or collimated, andthus converged or collimated light beams can be emitted.

Further, as shown in FIG. 3B, a plurality of optical lenses 21 eachhaving cut off the pair of flanges 48 as shown in FIG. 3A may beprepared and arranged into an array by bonding their second side faces45 and fourth side faces 47 to each other (optical lens arranging step).Since the flanges 48 have already been cut by the flange cutting step,an optical lens 31 having curved surfaces arranged with the same pitchwidth is formed by simply arranging the plurality of optical lenses 21while bringing their side faces into contact with each other (andbonding them). Since the adverse effects (such as deformation) uponheating in the drawing step are eliminated at the point of the opticallens 21, thus formed optical lens 31 is also free of the adverse effectsupon heating in the drawing step. The optical lens 31 in accordance withthe second embodiment comprises four optical lenses 21 arranged therein,and thus can respond to 4×4=16 incident light beams. Namely, it cancollimate or converge light beams from a light-emitting devicecomprising 16 light-emitting parts, and emit thus collimated orconverged light beams. Since the second side faces 45 and fourth sidefaces 47 are parallel to each other, an operation of arranging aplurality of optical lenses into an array while bringing them intocontact with each other is easily carried out.

FIGS. 4A and 4B are views showing effects of the methods of making anoptical lens in accordance with the first and second embodiments. FIG.4A shows an optical lens preform 140 in accordance with a comparativeexample, and a cross section of an optical lens 101 produced by drawingfrom the optical lens preform 140. FIG. 4B shows the optical lenspreform 40 in accordance with the embodiments, and a cross section ofthe optical lens 1 produced by drawing from the optical lens preform 40.

As shown in FIG. 4A, the optical lens preform 140 in accordance with thecomparative lens has no flange. Heating is likely to concentrate atcorner parts 49 of the preform, thus yielding a high temperature.Therefore, upon drawing, the curved surface parts 43 located at thecorner parts 49 are deformed under the influence of the heatingtemperature. Thus deformed curved surface parts 43 do not function as anoptically effective part as intended in the designing stage. Bycontrast, as shown in FIG. 4B, a pair of flanges 48 are formed on bothsides of the plurality of curved surface parts 43, i.e., at corner parts49 of the optical lens preform 40 in the methods of making an opticallens in accordance with the embodiments. Therefore, upon drawing, thepair of flanges 48 deform under the influence of heating in the drawingstep, whereby the form of curved surface parts 43 is kept even after thedrawing. Thus, in the methods of making an optical lens in accordancewith the embodiments, a pair of flanges 48 are provided, so as toreceive adverse effects due to the heating at the time of the drawingstep, thereby protecting the plurality of curved surface parts 43, whichwill function as optically effective parts after the drawing. Therefore,it is not necessary for the flanges 48 to have a flat form. For example,curved surface parts 43 formed in excess may be employed as flanges 48to be cut off when affected by the heating upon drawing.

FIG. 5A is a schematic sectional view of the drawing step in the methodof making an optical lens in accordance with the first embodiment,whereas FIG. 5B is a schematic sectional view of the drawing step in themethod of making an optical lens in accordance with a third embodiment.FIG. 5A is also a sectional view taken along the line IV-IV of FIG. 1B.In the drawing step in the method of making an optical lens inaccordance with the first embodiment, as shown in FIG. 5A, the electricfurnace 35 acting as the heating means is formed like a ring surroundingthe optical lens preform 40, and the ring is circular. Therefore, thedistance 71 from each corner part 49 to the electric furnace 35 isshorter than the distance 70 from each curved surface part 43 to theelectric furnace 35. Such a shorter distance to the electric furnaceacting as a heat source may cause the corner parts 49 to attain atemperature higher than that of other parts, thereby deforming thecorner parts 49 of the optical lens preform 40.

In the drawing step in the method of making an optical lens inaccordance with the third embodiment as shown in FIG. 5B, by contrast,the electric furnace 135 acting as the heating means has a formcorresponding to the cross-sectional form of the optical lens preform40, i.e., such a form that the side faces 44 to 47 of the optical lenspreform 40 have the same distance to the electric furnace 135 at anyparts, at the corners 49 in particular (the distance in this casereferring to the shortest distance to the electric furnace 135 withouttaking account of the curved surface parts 43 formed in the first sideface 44 and third side face 46). This prevents the corner parts 49 frombeing solely located closer to the electric furnace 135, whereby theheating temperature is evenly applied to the individual parts of theoptical lens preform 40 in the drawing step. Namely, this alsoameliorates inconveniences in which the heating temperature isconcentrated at the corner parts 49 so as to deform the optical lenspreform 40 in the drawing step. The electric furnace 135 having such aform is further effective when the optical lens preform 40 has ahorizontal size longer than the vertical size thereof.

Though the present invention is specifically explained in the foregoingwith reference to the first to third embodiments, the present inventionis not limited to the embodiments, which merely illustrate the bestmodes for carrying out the invention, but includes all the alterationsof the invention falling within the scope of claims of the invention andcan be modified in terms of form, size, arrangement, and the like.

For example, as in the optical lens preforms 340, 440, 540 shown inFIGS. 6A to 6C, single curved surfaces 343, 443, 543 may be provided.

Also, in terms of the flange form, the flanges may have projections 348,448 protruded from the curved surface parts 343, 443 as shown in FIGS.6A, 6B. In this case, upon drawing as shown in FIG. 2, the optical lenspreforms 340, 440 can stably be held by the rollers 33 by way of a pairof projections 348, 448, and thus can be prevented from wobbling at thetime of drawing. Also, the rollers 33 and the curved surface parts canbe kept from interfering with each other. Further, since the opticallenses 301, 401 made by drawing such optical lens preforms 340, 440 haveprotrusions corresponding to the projections 348, 448 of the preforms340, 440, the curved surface parts 343, 443 can be prevented from cominginto direct contact with an arrangement surface on which the opticallenses 301, 401 are disposed, side faces of members adjacent to theoptical lenses 301, 401, and the like. This makes the curved surfaceparts 343, 443, which act on light, harder to damage and so forth, andprevents performances of outgoing light from deteriorating.

Also, as in the curved surface part 443 shown in FIG. 6B, the curvedsurface part may be provided on one side alone. On the right side, FIGS.6A to 6C show respective optical lenses 301, 401, 501 formed by drawingthe optical lens preforms 340, 440, 540 shown on the left side.

As in the optical lens preform 640 shown in FIG. 7, each of the firstside face 644 and third side face 646 as a whole may be formed into aconvex surface. Here, when each of the first side face 644 and thirdside face 646 comprises a plurality of curved surface parts, each of thefirst side face 644 and third side face 646 is considered to be in aconvex surface form if a surface in contact with all of the plurality ofcurved surface parts is a convex surface. Though flat surface parts(first to fourth side faces) of an optical lens preform may deform toretract upon drawing, forming the first side face 644 and third sideface 646 into a convex surface beforehand yields an optical lens 601 (onthe right side of FIG. 7) having eliminated the distortion due to thedrawing.

The flanges of the optical lens preform shown in FIG. 7 also haveprojections 648 protruded from the curved surface parts. Therefore, whendrawn as shown in FIG. 2, the rollers 33 can stably hold the opticallens preform 640 by way of a pair of projections 648, whereby theoptical lens preform 640 can be prevented from wobbling at the time ofdrawing. Also, the rollers 33 and the curved surface parts can beprevented from interfering with each other. Further, the optical lens601 made by drawing such an optical lens preform 640 has projectionscorresponding to the projections 648 of the preform 640, and thus canprevent the curved surface parts from coming into direct contact with anarrangement surface on which the optical lens 601 is disposed, sidefaces of members adjacent to the optical lens 601, or the like. As aconsequence, curved surface parts acting on light are harder to damageand so forth, and performances of outgoing light are kept from lowering.

From the foregoing explanations of the invention, it will be obviousthat the same may be varied in many ways. Such variations are not to beregarded as a departure from the spirit and scope of the invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

INDUSTRIAL APPLICABILITY

In the method of making an optical lens in accordance with the presentinvention, the form of the optical lens, the form of the opticallyeffective part in particular, can be determined in the stage of thepreform before drawing, whereby the optically effective part can beprocessed in a sufficiently large size, and the form of the opticallens, the form of the optically effective part in particular, can easilybe shaped. This realizes an optical lens having an optically effectivepart accurately acting on light. Also, the burden on manufacture can bealleviated.

Further, in the optical lens preform, corner parts which are likely tobe influenced by heating in the drawing step so as to deform and soforth are formed with flanges, whereby each curved surface part actingas an optically effective part can be kept from being influenced byheating. This realizes an optical lens whose optically effective part isnot deformed by the drawing step.

1-11. (canceled)
 12. A method of making an optical lens comprising:producing the optical lens preform, the optical lens preform beingconstructed by a light-transparent material into a columnar formcomprising first to fourth side faces, at least one of the first sideface and the third side face opposite from the first side face includinga curved surface part formed parallel to a column axis, and a pair offlanges formed on both sides of the curved surface part; drawing theproduced optical lens preform; and producing an optical lens by cuttingthe drawn optical lens preform.
 13. A method of making an optical lensaccording to claim 12, wherein the producing an optical lens includescutting off the pair of flanges from the drawn optical lens preform. 14.A method of making an optical lens according to claim 13, wherein theproducing an optical lens includes preparing a plurality of opticallenses having the pair of flanges cut off, and arranging the opticallenses into an array by bonding the respective second and fourth sidefaces to each other.
 15. A method of making an optical lens according toclaim 12, wherein the drawing uses heating means with an annular formsurrounding the produced optical lens preform, the heating meanscomprising a ring form corresponding to a cross-sectional form in across-section perpendicular to the column axis of the optical lenspreform.